Abstract
In this study a systematic characterization of the kinetics and mechanics of fatigue crack propagation in crystalline poly(ethylene terephthalate) is presented. It is shown that the crack is accompanied by a large zone of transformed material. Based on the crack layer theory, the data of fatigue crack propagation are analysed. According to this theory, the specific enthalpy of damage is a material parameter, which is found to be about 2000 kJ m
−3. Also, a detailed description of the method of data analysis with respect to the crack layer theory is given.